S vstematy of Imlian Trees : Introduction. I. 



INDIA comprises a botanical region of essentially Asiatic and tropical con- 

 tinental area, ranging from primary evergreen rain-forest to the limit of Alpine plant- 

 life at the higher elevations of the Himalya, including sub-equatorial swamps, mountain 

 rain-forest and the deciduous monsoon-forest of drier central tracts, the vegetation of 

 grassy plains, estuarine mangrove-formation, sandy sea-coast, savannah and park- 

 lands, as well as tracts of dry arid sandy or stony desert, and affording examples of 

 all types of tropical vegetation and cultivation. 



Such may serve as an introduction to the optimum ecological regions of the 

 present world, on a scale and of a character wholly distinct from the impoverished 

 vegetation of more northern latitudes, and the mediocre types of European or indi- 

 genous fiora, which have long served as the elementary review of Systematic Botany. 

 Under such optimum conditions plant-life may be still dominant, as well as enor- 

 mously preponderant. !Much of the area has produced forest continuously throughout 

 known geological lime ; competition and natural selection continue to act on an inten- 

 sive scale. 



Botanical interest centres in forest-formation, as expressing the infinite possi- 

 bilities of combination of the same generalized features of somatic organization in 

 response to extreme biological factors as intensive insolation, problems of water and 

 food-salt supply, ])erennation over intense drought, the protection of the reproductive 

 processes and of the developing seeds, the possibility of dispersal to unoccupied 

 ground or of active competition in closed formations, and the critical stages of the 

 successful germination of the embryo, as also of its juvenile condition. 



The most characteristic feature is intense insolation, which gives practically 

 unlimited supplies of photosynthetic carbohydrate, in excess of the possible capacity 

 for further proteid-syntliesis, dependent in turn on the food-ions of the water-supply. 

 Waste polysaccharide is utilized in timber-production and xerophytic protective 

 mechanism of sclerosed strands and layers, conspicuous also in massive capsules 

 or sclerosed indehiscent fruits, as again in the production of starch or hydrocarbon fat 

 and oil, giving enhanced possibilities of ' food-storage ' for embryos in germination, or 

 again as the sugars and organic acids of large succulent fruits utilized for the dis- 

 persal of seeds by animal agency. 



Increased rates of metabolism follow higher temperatiu'e. Foliage-leaves may 

 be reckoned in feet instead of inches, and the same applies to the development of the 

 annual shoot. Flowers range to hur;e mechanisms, or may be reduced to the merest 

 vestiges of economized systems. Pollination by bee-agency is less predominant in 

 forest-formation ; small mechanisms are associated with flies and insects with short 

 proboscides ; larger mechanisms grade to moth and bird-visitation. 



Water-supply, regarded not only as the essential component of the dilute 

 medium of living plasma, but also as the source of food-ions, is the primary 

 factor in promoting ecological formations, and determining the evolution of types of 

 higher grade, according as the supply may be permanent, casual, seasonal, or practi- 

 cally non-existent. Methods of economizing the available supply become the rule, as 

 few plants do not feel the strain at some time of the year, day, or of their individual 

 life. Similarly all advancing stages of the ovary-chamber, which marks the evolution 

 of the Angiosperm gynoecium, from the primary closing in of free megasporophylls to 

 phases of syncarpy and the elaboration of the inferior ovary, are to be approached 

 from this standpoint. The case of the ' green-fruit ' affords conspicuous illustration. 

 Ill evergreen rain-forest, flowers and fiuits of the upper exposed levels, competing 

 with the foliage-leaves for water-supply, present advanced xeromorphic mechanism. 

 In seasonal deciduous monsoon-forest green fruits subserve seed-protection into the 

 driest months of the year, with increased devices of osmotic water-storage, sclerosed 

 layers of massive ovary-wall, packing of the internal cavity with dry or succulent hair- 

 growths, succulent seed-arils, or lamellar extensions, the production of terpenes, 



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